Process for preparing perfluorinated linear polyethers

ABSTRACT

PERFLUORINATED CYCLIC ETHERS AND FLUORINATED LINEAR POLYETHERS ARE PREPARED BY PHOTOCHEMICAL REACTION IN LIQUID PHASE OF PERFLUOROPROPYLENE WITH OXYGEN IN PRESENCE OF ULTRAVIOLET RADIATION.

United States Patent US. Cl. 204-158 12 Claims ABSTRACT OF THEDISCLOSURE Perfluorinated cyclic ethers and fluorinated linearpolyethers are prepared by photochemical reaction in liquid phase ofperfluoropropylene with oxygen in presence of ultraviolet radiation.

CROSS REFERENCE TO RELATED APPLICATION This application is a division ofcopending application Ser. No. 650,257, filed June 30, 1967, nowabandoned, which application is in turn a continuation-in-part of ourUS. patent application Ser. No. 446,292 filed Apr. 7, 1965, now US. Pat.3,442,942, issued Apr. 7, 1969.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to a process for preparing new products consisting essentiallyof carbon, fluorine and oxygen atoms having the structure of linearpolyethers or of cyclic ethers, and to a new method for the preparationof epoxide of perfluoropropylene, COF and CF COF.

Chemical resistance and thermal resistance are two of the mostattractive and appreciated characteristics of fiuoro-organic compoundswhich contain .a high percentage of combined fluorine in theirmolecules. Because of these and other favorable physico-chemicalproperties, the fiuorinated compounds are of great interest and havefound numerous useful applications.

For many of these applications, fluorinated substances containingchemically reactive functions, e.g., double bonds, carboxy groups andtheir derivatives, carbonyl groups etc., in their molecules are highlydesired. These reactive groups permit various subsequent transformationsof these molecules, which determine their particular physico-chemicalcharacteristics and make possible their chemical interaction with othermolecules.

For other applications, e.g., for use as fluids for heat transfer, forlubrication under particular conditions, or for electric insulation,there are required high molecular weight fiuorinated compounds which (1)are liquid over a wide range of temperatures, (2) have a relatively lowvapor pressure and (3) exhibit a high degree of chemical and thermalstability. For these and other applications, perfluorinated products arehighly suitable, i.e., products which do not contain appreciable amountsof elements other than carbon and fluorine and, in particular, do notcontain hydrogen in their molecule. Such perfiuorinated products, infact, generally possess the highest characteristics of chemical inertiaand often of thermal stability.

(2) Description of the prior art It is known that fiuorinated andperfiuorinated products having a rather high molecular weight can bereadily obtained by polymerization and copolymerization of fluoro- "iceand perfluoro-olefins. Usually, however, the products thus obtained arehigh polymers having the appearance and characteristics of solidsubstances, either at room temperature or at somewhat highertemperatures. Accordingly, they are unsuitable for most of theapplications referred to above, wherein it is necessary to employmaterials having a low volatility but being liquid at room temperatureand over a wide range of temperatures.

Attempts have been made to obtain high molecular weightfluorine-containing products possessing these characteristics bytelomen'zation reactions of fluoroolefin. By this type of reaction, forwhich considerable descriptive literature exists, various products wereobtained. The chemical structure of these products can be represented bythe general formula X(A),,Y, wherein X and Y areatoms or atom groupsderived from the telogenic agent XY employed. A is a combined unit ofthe fluoroolefin, and n is an integer between 1 and 100.

However, the telomers that can be obtained from the fluoroolefin, and inparticular from fiuoroethylene, which as a practical matter are the onlytelomers that can easily be obtained, exhibit a significant drawbackwhich hinders their use for many of the desired applications. Thus, themolecules of the telomers consist essentially of a regular sequence ofequal (A) units bound one to another by carbon to carbon bonds. Thisimparts to the molecules a considerable rigidity and a high tendency tobecome crystallized. It is also known that rotation around the C--Cbonds is hindered by a strong energy barrier, in contrast to thecondition existing with C-O bonds. Thus, C-O bonds have a considerablefreedom of rotation. It is also known that the linearity and regularityof structure of the macromolecules appreciably promotes thecrystallization process. Consequently, when a telomer of, for example, afluoroethylene has a value n sufiiciently high to render its vaporpressure negligible or very low, it is normally a solid or a Wax at roomtemperature. When the telomer is brought to the molten state by heating,it generally becomes a highly volatile liquid, having a low viscosityand a high variation of viscosity with temperature, so that it is,accordingly, unsuitable for most of the desired applications.

It is known, for example, from Belgian Pat. 616,756, and French Pats.1,359,426 and 1,362,548, to prepare perfluoroethers by polymerisingepoxides of perfluoroolefins in the presence of active carbon oralkaline catalysts. The products thus obtained arepolyperfluoroalkylenethers having a thoroughly regular structure asregards both the units forming the chain and their distribution and arecharacterized by the fact that each of their two terminal groups is thesame in all chains. These products consist of chains wherein 0-0 and C-Cbonds are regularly alternated (-CCOOOO). As noted above, C-C bonds havea marked energy barrier which tends to oppose their rotation whereasthis is not the case for CO bonds.

It is desirable, moreover, to have available products having a higherincidence of C--O bonds with respect to C--C bonds in the polymericchains. Furthermore, it is desirable to have available productscontaining peroxidic groups.

SUMMARY OF THE INVENTION We have found that it is possible to obtainproducts having good dielectric, viscosity and lubricatingcharacteristics, and which, because of the possibility of a higherincidence of C-O bonds with respect to C-C bonds, may have improvedproperties as regards variations of viscosity with temperature, by meansof direct reaction of perfluoropropylene with molecular oxygen underultraviolet radiation. Stable products having a very high molecularweight and containing only carbon, fluorine and oxygen atoms in theirmolecules are obtained. Their structures vary depending upon thereaction conditions, and they consist of chains wherein there can bepresent sequences of C-O bonds and also of OO-- bonds, and differentterminal groups. Said products are obtained according to the presentinvention by means of direct reaction of perfluoropropylene withmolecular oxygen or with a gas containing oxygen, by operating in theliquid phase, at temperatures between -100 and +80 C., under a pressurebetween 0.1 and 40 atmospheres (preferably between 1 and 10atmospheres), in the presence of ultraviolet radiations, at least 1% ofwhich radiations have a wave length lower than 3300 A.

The products produced by the process of this invention includeperfiuoropropylene epoxide, COF

cyclic perfiuorinated ethers having the formula m-o F-C F in which R maybe F or CF and linear perfiuorinated polyethers and mixtures thereof ofthe general formula (CF: )8 II wherein: C F is a perfiuoroalkylene unitderived from the opening of the double bond of a hexafluoropropylenemolecule, the different perfluoroalkylene units having a randomdistribution along the polyether chain. A as a functional group selectedfrom the group consisting of -COF, --OF COF and CF(CF )COF, and P, Q, -Rand S may be the same or different numbers, Q, R, and S may each or allbe equal to zero, the sum of P+Q+R being a number between 1 and 100, theratio (Q+R)/P being a number between zero and 2, and preferably betweenzero and 1, the ratio varying between zero and 0.5, the ratio S/P beinga number between zero and 1, preferably between zero and 0.5. Wheninteger S is zero, the linear perfiuorinated polyethers (II), forsufiiciently high values of P, will exhibit the structure of truehomopolyethers when Q and R in the above formula are zero, an are to beregarded as true copolymeric polyethers or copolyethers whenperfluoroalkylene units different from C F are also present in thechain, i.e. when Q or R or both of them are different from zero.

It is to be noted that linear perfiuorinated polyethers conforming tothe foregoing Formula 11 may possibly contain therewithin units of C 1bonded directly to one another. Any such units are present in extremelyminor amounts, i.e., less than about two percent by weight, and ifpresent do not affect the properties of the polyethers.

The products produced by the process of the present invention aredescribed in greater detail in application Ser. No. 650,257, of whichthis is a division and in application Ser. No. 31,852, filedconcurrently herewith, the contents both of which are herebyincorporated herein by reference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of the presentinvention comprises subjecting perfluoropropylene, in the liquid phase,either alone or diluted with an inert solvent, to a photochemicalreaction with molecular oxygen at a temperature between about -100 C.and +80 C., at a pressure between about 0.1 and 40 atmospheres, in thepresence of ultravio et radiation containing at least 1% of radiationhaving a wave length less than 3300 A., the oxygen being fed to theliquid reaction phase in such amount as to maintain the liquid phasecontinuously saturated with oxygen.

In order to maintain perfluoropropylene in the liquid phase at thetemperature selected for the reaction, a sufiiciently high totalpressure (which can be as much as 40 atmospheres) is used. As can beseen from the experi mental examples reported hereinafter, in the rangeof preferred temperatures, the pressure under which the reaction iscarried out does not markedly influence the chemical structure of thereaction product. However, the pressure must be such as to maintain inthe liquid phase at least most (i.e., greater than 50 percent andpreferably greater than percent) of the perfiuoropropylene present inthe reaction zone and the partial pressure of molecular oxygen must beat least 0.1 atmosphere.

The process may be conveniently carried out by passing a stream ofmolecular oxygen or of an oxygen-containing gas such as, for example,air through a liquid phase of hexafiuoropropylene, in the presence ofUN. radiations as previously defined.

Within the scope of our process, one can select operating conditionswhereby there is obtained a high degree of specificity towards theformation of one type of product rather than of another among theproducts previously defined.

For example, a high specificity toward the formation of the epoxide of CF can be obtained, that is a ratio between the epoxide and the highermolecular weight compounds of about 1:1 (50% epoxide) or more, when theprocess is carried out under pressure, preferably in excess ofatmospheric, and at a temperature close to the boiling point of theliquid phase under such pressure. Conversely, the ratio between theepoxide and other reaction products having higher molecular weightdecreases, and can be less than 0.01:1, as the operating temperature ofthe process is decreased, thus increasing the difference between thetemperature employed and the boiling temperature of the system under theadopted pressure.

The structure of the linear polymeric products and mixtures thereofincluded in the general 'Formula II are highly influenced by two mainparameters of the reaction: (1) the temperature and (2) the irradiationintensity of the liquid reaction phase. By appropriate selection of theoperating conditions for these two parameters it is therefore possibleto direct the reaction toward the formation of one type of productrather than toward another.

It has been found that essentially polymeric products are obtained, ofthe formula wherein P, S and A are as previously defined, by carryingout the reaction at temperatures lower than about l0 C., and preferablybetween about -80 C. and 40 C. Indeed, in the lowest range oftemperature the content of perfiuoroalkylenoxy units other than -C F-O-- in the molecular chain of the resulting polyethers is so low as tohave virtually no appreciable influence on the properties of theproducts, and these products may be considered to be of thehomopolyether type.

When the reaction is carried out at a temperature of about 10 0., thereare present in the mixture of final polyethers minor amounts (about 2-3%by mols) of other perfluoroalkyleneoxide units different from theprincipal unit -C F 0. When operating at higher temperatures, andparticularly at temperatures higher than 0 C., the percentage of unitsof -C F1O-- and/or C F-0- (IJF: in the reaction product increases. Thus,the higher the temperature, the higher the percentages of such otherunits, so that these units become a very important characterizingfeature of the copolyether chains. Thus, by operating at increasinglyhigher temperatures and approaching the limit of about 80 C., thecopolyether reaction products will contain up to 66% by mols of units.

Thus, when a temperature above l C. is used, the average molar ratiobetween the units -CF2OBI1d-CFO and the units --C F O--, will have avalue within the limits of 0.02 and 2. This ratio, as will also be seenin the following experimental examples, increases upon increasing thereaction temperature.

In addition, the temperature very markedly influences the averagemolecular weight of the polymeric products, that is the value of the sumof P+Q+R. The higher average molecular weights will generally beobtained at the lower temperatures whereas lower average molecularweights are obtained by operating at higher temperatures.

Moreover, it is also possible to regulate the average molecular weightin order to obtain the desired value by varying the concentration of C Fin the liquid phase. The higher molecular weights are obtainable byusing a high concentration of C 1 for example by using undiluted C Fwhereas lower molecular weights are obtained by diluting the C 1 with asolvent.

The concentration of peroxidic groups depends on the intenstity ofirradiation and can be varied within the limits desired by utilisingsuitable average irradiation conditions in the reaction zone. Theconcentration of the peroxidic groups depends also on the degree ofconversion actually obtained during the reaction.

The average intensity of irradiation of a reaction system is in generala quantity that is diflicult to define by numbers, since it depends onseveral parameters and is highly influenced by the particular geometryof the reaction system. A meaningful indication of the average value ofthe irradiation intensity in a sufliciently symmetric reaction systemcan, however, be inferred from a consideration of three fundamentalelements:

(1) the amount of useful U.V. radiations having a wave length lower than3300 A. penetrating the reacting phase, E (watts);

(2) the surface through which the radiations penetrate reaction system,S (cm?); and

(3) the volumes of the reaction system, V (cm.-*).

If we consider, for example, the particular instance in which the U.V.radiation source is placed completely inside the reaction system and thesurface S consists of a material that is completely transparent to theuseful U.V. radiation, the value of E can be considered as equal to theamount of radiation, having useful wave length, emitted by the source.If on the contrary, either because the U.V. source is placed outside thereaction system or because between the U.V. source and the reactingsystem there is placed a medium having a certain absorption power forthe radiations, so that only a portion of the useful radiations emittedby the source reaches surface S or in any event penetrates the reactionsystem, the value of E can then be calculated, either through a simpleconsideration of geometric factors or by a real measurement of thequantity of useful radiations as can be obtained by having resource toactinometric methods, well known to people skilled in the art.

The value of surface S must be considered in an appropriate manner,namely, by referring to the geometric surface of an ideal type whichmost nearly could be compared with the actual surface.

In other words, the value of S must be calculated without taking intoaccount surface irregularities or slight differences with respect to theperfect geometrical form. The reaction volume must be considered asequal to that which can be actually reached by the U.V. radiations,Without taking into account the possible phenomena of absorption of theradiations by the liquid medium.

We have observed that, in order to represent in a meaningful way thesituation of average irradiation which characterises a particularreaction system and which would directly influence the formation ofrelatively more or less preoxidised reaction products, one may havereference to an average irradiation index I, which is defined by theequation E (watt/cm?) wherein E, S and V have the aforedescribedmeaning.

We have ascertained that it is possible to obtain, from liquidperfluoropropylene and oxygen, reaction products having a desiredcontent of peroxidic groups by using an average irradiation index offrom 0.1 to 50 watts/cm. A low content of peroxidic oxygen, i.e. S/(P+Q+R+l) less than 0.2, is obtained by adopting reaction conditionswhereby index I is greater than 2 and preferably greater than 3. On thecontrary, with values of I less than 2, or preferably less than 1,polyesters containing substantial amounts of peroxidic groups, that isS/(P+Q+R+1) greater than 0.2, can be obtained.

It should be noted, however, that not only the irradiation conditionsinfluence the extent of the peroxidic nature of the reaction products.Thus, other reaction conditions, such as, for example, the degree ofconversion, will also affect this characteristic of the products. Moreparticularly, it has been ascertained that even in the presence of asufficiently high average-irradiation intensity (I greater than 2), thepolyether products formed in the initial step of the photochemicalreaction between liquid perfluoropropylene and oxygen may contain aconsiderable quantity of peroxidic groups. The average content ofperoxidic oxygen of the products decreases rapidly, however, as thereaction progresses, so that, when, for example a conversion higher than5-10% of the perfluoropropylene initially present in the reaction zoneis reached, the peroxidic content reaches a practically constant valuethat can be either zero or very slight, depending upon the particularvalue of I. Conversely, even by using a rather low intensity ofirradiation, for example, lower than 1, it is possible to obtainpolyethers having a reduced content of peroxidic oxygen, such asS/(P+Q+R+1) lower than 0.2, by carrying out the reaction to a high finaldegree of conversion, for example, of the order of 60-70%.

The statements previously made relating to the effect of theaverage-irradiation intensity on the peroxidic character of the reactionproducts should, in a strict sense, actually be confined to the productsobtained at conversions not less than about 5% and not greater thanabout 70%.

Additionally, it has been ascertained that the reaction temperatureexerts a certain influence on the characteristics of the products, inthe sense that by lowering the reaction temperature below about 65 C.,the irradiation conditions being the same, the reaction products tend tohave a higher content of peroxidic groups.

As regards the amount of oxygen to be employed in order to maintain theliquid reaction phase saturated with oxygen, it was ascertained that anexcess of oxygen should be used with respect to the amount of oxygenconsumed during the reaction. In other words, the rate of oxygen fedinto the reaction zone should exceed the rate at which the oxygen isbeing consumed during the reaction.

'For example, when operating at about atmospheric pressure, the excessof oxygen in the liquid reaction phase can be obtained by bubbling intothe reaction mixture an amount of oxygen, either in the pure state ordiluted with an inert gas, that is at least twice that amount that issimultaneously being consumed. The excess of oxygen leaving the reactorcarries along such volatile reaction products as COF: and CF -COF. It isalso possible to operate without having an outflow of oxygen from thereactor. In such instance, in order to operate in the presence of anexcess of oxygen, it is necessary to maintain a high oxygen partialpressure in the reactor while the reaction is carried out. This can beobtained, for example, by operating at low temperatures (of the order of40 to 60 C.) and at a pressure higher than atmospheric, preferably above4 to 5 atmospheres and by continuously maintaining such pressure so asto replenish the amount of oxygen consumed. In this instance, the highpressure maintains the partial pressure of the volatile reactionproducts in the vapor phase at a low value, so as not to disturb thereaction that thus can continue so long as there is oxygen available inthe liquid mixture, that is, the oxygen concentration in the liquidmixture is maintained at saturation.

We have also found that it may be convenient to carry out thephotochemical reaction between oxygen and perfluoropropylene in thepresence of a liquid phase by adding to the reaction system anothercompound which is liquid under the reaction conditions. This diluent maybe any of various compounds which do not appreciably react with oxygenunder the selected irradiation conditions. The diluent may or may notact as a solvent for either the perfluoropropylene used in the reactionor for some or all of the reaction products.

Compounds which are suitable for this purpose include, for example,perfluoro compounds such as perfluorodimethylcyclobutane, liquidperfiuoroparaffins, perfluorocyclobutane, perfluorobenzene,perfluoroamines such as triperfluorobutylamine, straight chain or cyclicperfluoro ethers, such as, for example, perfluoropropylpyrane, andoxygenated perfluoro compounds which may be obtained according to thepresent process, such as hexafiuoropropylene epoxide. In addition,wholly or partially chlorinated compounds may be used as the reactionmedium, for example, carbon tetrachloride, chloroform, methylenechloride, methylchloroform, and chlorofluoro derivatives of methane,ethane and propane, such as CEO, CF CI CFCl CHF CI, CHFCI CF ClCF-,-Cl,CFCIQCFQCI, CCl ---'CF,, CF Cl'CH CF OFClCF Cl, etc.

The reaction may be carried out according to an essentially 'batchwisetechnique. In such case, into a reactor containing the initial charge ofliquid perfiuoropropylene, either in the pure state or in solution inpreferably perhalogenated solvents, at the pressure and temperatureconditions selected for the reaction, with irradiation by means of anUV. light from a suitable source such as a mercury vapor lamp, there isintroduced a stream of molecular oxygen or of a gas containing molecularoxygen such as air, such introduction preferably being across the entireliquid phase. The excess oxygen leaving the liquid phase is saturatedwith perfluoropropylene and also contains most of the low molecularWeight degradation products and other volative reaction products suchas, for example, the epoxide C F O. By means of a suitable refluxcondenser, most of the entrained penfluoropropylene is removed andrecycled back to the reaction zone, while the low molecular Weightproducts having an acidic character are separated from the oxygen bywashing with water or an alkaline solution.

The thus purified oxygen, after careful drying, may be recycled to thereaction together with added oxygen to replace the amount alreadyconsumed in the reaction. The reaction is carried on under the forgoingconditions until the conversion of the desired amount of initialperfluoropropylene is reached. Thereafter, the U.V. irradiation isstopped and, by distillation of residual perfluoropropylene, if present,and of cyclic perfluorinated ethers, there is obtained as the residuethe higher molecular weight linear reaction products in the form of acolorless viscous oil.

It is also possible and frequently preferable to carry out the reactionin a completely continuous manner so as to obtain higher homolog (highermolecular weight) reaction products. In such instance, a portion of theliquid phase present in the reaction zone is continuously removed fromthe system. By suitable means, for example, by distillation,perfluoropropylene is separated from the reaction products in suchportion and is continuously rec'ycled to the reactor while the amount ofperfiuoropropylene consumed by the reaction is taken into account andadded as make up.

Cyclic ethers obtained in accordance with our process include C F Operfiuoro-4-methyl-1,3-dioxolane (B.P.

and C F O perfluoro-2,4-dimethyl-1,3-dioxolane (B.P. 32.5" C.)

CFs-(F F-C F:

I CF;

These two cyclic ethers are new chemical products characterized byextremely high chemical and thermal resistances.

The fields of applications of the products of the process of the presentinvention are remarkably wide due to their chemical structure.

For instance, those products containing a high content of peroxidicgroups find utility as cross-linking agents for elastomeric polymerssuch as fluorinated polymers and copolymers, for example, copolymers ofvinylidene fluoride and hexafiuoropropylene.

The non-peroxidic polyethers are liquids which, depending upon theirmolecular Weights, may have a boiling temperature from as low as of theorder of 10-20 C., under normal pressure (low molecular weightmaterials) to more than 200 C. under reduced pressure of 1 mm. Hg (highmolecular weight materials). They have very high chemical and thermalstability and exhibit very good lubricating properties. For thesereasons they may be used as hydraulic fluids, heat exchange liquids,and/or as lubricants under particularly severe temperature conditions.

For certain applications, such as those involving use at very lowtemperatures (down to l00 C.) and those wherein only a very lowvariation in the viscosity at different temperatures is permitted, thecopolymeric poly ethers are preferred over the homopolymeric polyethers,since the former show a higher incidence of C0 bonds in the oligomericchain. This leads to a lower rigidity in the molecular structure, withthe advantage that the products exhibit a lower viscosity at a givenmolecular weight, or a lower volatility at a given viscosity.

Another advantage is afforded by virtue of the low variation inviscosity with temperature. It is well known that, whereas C-C bondshave a marked energy barrier which tends to oppose their rotation, thisis not the case for CO bonds, and therefore a higher ratio bonds in themain chain causes the above described effects. Homopolyethers are thuspreferably used for those applications wherein an extreme chemical andthermal stability and therefore a lower -C-O/CC- bond ratio is required,such as applications for heat-transfer and lubrication under conditionsof high temperatures, high pressures and/ or in the presence of stronglyreactive chemicals.

The cyclic ethers can be used as solvents or plasticizers forhalogenated organic compound generally, and, in particular, forfluorinated organic compounds.

The following examples will further illustrate our invention. All partsare by weight unless otherwise stated.

EXAMPLE 1 An apparatus 'was set up consisting of a three-necked glassflask having a capacity of 1.5 liters and provided with a thermometer, agas inlet dipping tube reaching the bottom and an outlet communicatingwith the atmosphere through a reflux condenser cooled by a coolingmixture maintained at 78 C.

Into the reactor there was introduced a quartz ultraviolet ray lamp ofthe Original Hanau Q81 type, having a tubular shape and a size of 245 x20 mm. This lamp had an absorption of 70 watts and generated awave-length emission mainly between 2400 and 4400 A., amounting to 12.8watts. In such emission the radiations having a wave-length lower than3300 A. correspond to 3.8 watts. The calculated index I was between 3.5and 4. 1230 g. of pure perfluoropropylene were condensed into thereactor, which was maintained by external cooling means at a temperatureof 78 C.

While maintaining the external cooling so as to keep the temperature ofthe liquid between 60 and 30 C., the UV. lamp was switched on. By meansof a circulation pump, a stream of anhydrous oxygen (130 l./h.) was sentthrough the inlet pipe dipping down to the bottom of the reactionvessel. The gas leaving the reaction vessel after having passed throughthe reflux condenser was washed with an aqueous KOH-solution having aconcentration of 20% and then collected in a 50 liter gasometer fromwhich, after drying, the gas was once more picked up by the pump andrecycled into the reaction zone. Oxygen in an amount equivalent to thatconsumed in the reaction was periodically fed to the gasometer.

After 28 hours, about 75 NI (liters under normal conditions) of oxygenwere absorbed and the reaction was stopped. The unreactedperfiuoropropylene and those reaction products having a boilingtemperature below 30 C. at atmospheric pressure were separatelydistilled and removed from the reaction vessel. 650 g. of a mixturecontaining 78% by weight of C F and 19% by weight of perfluoropropyleneepoxide (B.P. 29 C.) were thus obtained.

The liquid reaction products amounted to 650 g. and had the appearanceof a colorless, transparent, viscous oil.

The percent composition of this product was:

and the corresponding average empirical formula was (C F O wherein n wasfound by determination of molecular weight to be about 20-22.

The N.-M.R. spectroscopic determination was in agreement with theaverage formula I CF;

F3O(C3FQO)P'(C Fio c F-O (O)A wherein A is COF the ratio of the twofluoroformate isomer groups,

0 Fz-C F-o-o 0 F and 0 FC Fr-O-C 0 F, being 3:1

CF: 6F:

Distillation interval Fraction Fractions (a), (b) and (c), which wereliquid, had sharp, acrid odors and developed hydrofluoric acid fumeswhen exposed to moist air. They were miscible in ethyl ether.

Fractions (d) and (e) were combined and the mixture was subjected tocareful fractionation in a rectifying col-. umn while operating under aresidual pressure of 10 mm. Hg. In this way, the fractions reportedhereinafter in Table 1 were separated. In this table there are alsoreported data relating to density, viscosity, equivalent acidimetricweight, and percentage composition determined on various fractions.

The infrared absorption spectra of the various fractions all weresimilar one to another, presenting absorption bands in the 5.25,:4 zoneand in the 5.6 zone, due to the presence of COF and COOH groups,respectively. The intensity of these absorption bands decreased for thevarious fractions as the boiling temperature increased.

Other infrared absorption bands present in all the fractions occured inthe zones between 7.5 and 9.2 1. and also at 10.15, 11.2, 11.5, 12.05,12.35, and 13.4

Solubility tests of the various fractions in ethyl ether showed thatwhile fractions 1 and 2 could be mixed in all ratios with ethyl ether,fractions 10 and 11, on the contrary, were practically therewithimmiscible. The other fractions showed intermediate miscibility.

All of these fractions were completely miscible in all theperfluorinated solvents examined.

Fraction (f) had an average density 11 of 1.8953 and an averageequivalent acidimetric weight of about 4000, as determined in an aqueousNaOH solution in accordance with the conditions described in Table 1.The average percent composition was: C =21.6%; F 68.5%; O: 9.9%.

In fraction (f) the following viscosities were determined at varioustemperatures:

The infrared absorption spectrum of fraction (f) revealed, besides thepresence of small absorptions in the zones of the --COF and COOH groups,a wide absorption hand between 7.5 and 9.2 1 with a maximum of about8.0a, and other characteristic absorptions at 10.15, 11.2, 11.5, 12.05,12.35, and 13.4,u.

50 g. fraction (f) were heated with 5 g. of KOI-I in the form of pelletsfor a period of 2 hours at a temperature of 240-250 C. at atmosphericpressure, in a -cc. flask which was part of a distillation apparatus.During this treatment, the development of carbon dioxide, fluoroform,and water vapor was observed. At the end of this treatment, the contentsof the vessel were subjected to vacuum distillation. About 40 g. ofcolorless, transparent oil having a boiling range between and 200 C. at0.2 mm. Hg were thus obtained. This product no longer showed an acidcharacter, was completely non-reactive towards water and alkalinesolutions, and had an infrared absorption spectrum in which theabsorptions due to the acid functions were completely absent.

Its average molecular weight was determined to be of the order of 3000.

By N.*M.R. analysis the chain was shown to consist essentially of thesame structure as the starting product, except that the terminal group A(fluoroformate isomer groups) had become a mixture of C'F H and 11CFH-CF in a ratio of about 3:1. The terminal group --'O CF H wasrevealed by the resonance bands of 2 atoms of fluorine at +83.3 p.p.m.from CFCl The terminal group O-CFH--CF was revealed by the resonancebands of 3 fluorine atoms at +85 p.p.m. and of 1 atom of fluorine at+146.2 p.p.m.

The residual fraction (g) had a viscosity at 24 C. higher than 2000centipoises, and a density d of 1.9104. It showed an exceptionalresistance to thermal treatment, both in air and under high vacuum,without indicating any symptom of modification in structure afterprolonged periods of heating at temperatures of about 400 C. The averagepercent composition was: O=21.5%; F=68.7%; O=9.8%. The infraredabsorption spectrum of this fraction was completely similar to that ofthe preceding fractions, except for the very low intensity of theabsorptions corresponding to the acid groups.

Fractions (f) and (g) were miscible in all proportions with all theperfluorinated solvents examined, such as, for example,perfluorocyclobutane, perfluorotributylamine, and perfluoropropylpyrane.They were, by contrast, immiscible with conventional organic solvents,such as, for example, acetone, ethyl ether, tetrahydrofurane, toluene,C01 CHCI CH Cl ,.dioxane, dimet hylsulfoxide, dimethylformamide, ethylacetate, etc.

Iodometric analysis showed the presence of active oxygen in amountscorresponding to a ratio S/(P+Q+R+1) of 0.03.

The product gave the following fractions when subjected to distillation:

Fraction Weight (g.) Distillation interval 11. 6 2590 C./760 mm. Hg. 20.3 9D160 C./760 mm. Hg. 29 2 50-100 C./0.2 mm. Hg. 15. 2 100150 C./0.2mm. Hg. 12. 8 ISO-280 C./0.2 mm. Hg.

3 0 Residue.

The products obtained, for the same distillation interval, showedcharacteristics equivalent to those of the products obtained inExample 1. As can be seen, the presence of a solvent during the reactionresulted in the formation of a product having a lower average boilingtemperature.

EXAMPLE 3 TABLE 1 Distillation Equivalent Viscosity Percentagecomposition interval, 0., acidimetric (centipoises) Number of fractionsg. at 10 mm. Hg du weight 1 at 24 C. C F

1 The equivalent weights reported were obtained by introducing about 0.4g. of exactly weighed product into 25 cc. of 0.1 N NaOH keeping thewhole in strong agitation for 2 hours at room temperature and titratingback with 0.1 N HCl using phenolphthalein. In the thus neutralizedsolution, the F ions present were determined with thorium nitrate. Theratio between the weight in grams of the startlng product and the dficrence between the number of acid equivalents of the product and thenumber of the equlvalent of fluorine ions was considered as theequivalent acidimetric Weight.

EXAMPLE 2 The same apparatus as in Example 1 was used, except that acylindrical glass vessel having a volume of 0.4 liter, in which theU.V.-ray lamp was contained, was used as the reactor. 165 g. ofperfluoropropylene and 200 cc. of perfluorocyclobutane were collected inthe reaction vessel by distillation and condensation at -78 C. Thereaction was started by passing into the reactor an oxygen stream (about50 l./h.) and activating the U.V.-lamp, with the temperature at C. Thereaction was continued for a period of 11 hours, during which time thetemperature of the liquid phase gradually rose until it reached 9 C. anda total of about 18 N liters of oxygen were absorbed.

Under these conditions the value of the index I was greater than 5.

C F the unreacted perfluoropropylene, and those products having aboiling temperature lower than 25 C. at atmospheric pressure weredistilled off. The residue consisted of 95 g. of a liquid product havingthe average percent composition and the average molecular weightcorresponding to (C F O wherein n is about 14-16. The N.M.R.spectroscopic analysis indicated that the product had an average formulawherein the ratio (Q+R)/P was about 0.05, the ratio R/Q was about 0.1,and A was essentially the COF group.

action was stopped and, after removal by distillation of the productswhich were volatile at room temperature, two liquid layers resulted. Thelower liquid phase (about 25 g.) was separated and gave fractions ofproducts having boiling temperatures between 40 C./760 mm. and 230C./0.3 mm. when distilled. The upper liquid layer gave, after removal ofCCl,;, 8 g. of liquid products containing only C, F and O and havingboiling temperatures between and 210 C./760 mm. At the same boilingtemperature, the products obtained showed characteristics completelyequivalent to those of the products described in Examples 1 and 2.

EXAMPLE 4 A photochemical reaction between C F and oxygen was carriedout with conditions analogous to those of the preceding example, exceptthat 275 g. of methylene chloride were used as the diluent in lieu ofCCI After a 6 hour reaction period, the two liquid layers present in thereaction medium were separated and distilled. A total of 28 g. offluoroxygenated products were obtained,

which products had a distillation interval between 45 C./760 mm. Hg and250 C./0.6 mm. Hg and which exhibited properties very similar to thoseof the products obtained in the preceding example.

EXAMPLE '5 An apparatus was assembled consisting of a cylindrical glassvessel having a capacity of 0.4 liter and provided with a thermometerand a gas inlet tube dipping down to the bottom and an outletcommunicating with the atmosphere through a reflux condenser cooled at78 C., and containing an ultraviolet-ray lamp of the type defined inExample 1. Into this vessel, 460 g. of C F were distilled and condensedat 78 C. and the photochemical reaction was started by irradiation withultraviolet light and by feeding a stream of dry air (60 l./l1.) to theliquid phase kept at -70 C. The air left the reactor and was removedafter passage through the condenser at 78 C. which recycled at least aportion of the entrained C 1 back to the reactor. As the reactionproceeded, the temperature of the liquid phase rose gradually until itreached 25 C., after about 8 hours of reaction. The liquid productremaining in the reactor (108 g.) was distilled and separated into thefollowing fractions:

30-57 C. [760 mm.

res-260 (346.3 mm. (E) 25 grams Residue.

This example illustrates how one may directly obtain a polyperoxide ofperfluoropropylene by reacting the olefin with oxygen in the presence ofU.V. radiations of an appropriate spectrum. For this purpose there wasused a low pressure mercury-vapor quartz generator of the NK6/20 Hanautype, having an emission spectrum containing a high percentage ofradiations having a wavelength lower than 2,000 A. and an absorption of8 watts. In this lamp, those radiations having a wave-length lower than3300 A. corresponded to 0.9 watts when working at room temperature. Thissource of U.V. light was contained in a tubular quartz sheath having asize of 245 x 20 mm. and was immersed into 490 g. of liquidperfiuoropropylene placed in a 0.6 liter glass vessel provided with aclipping tube for the introduction of oxygen, and a reflux condenserkept at 78 C., which vessel was immersed in an outer cooling bath. Withthis experimental apparatus, the irradiation index I was calculated tobe less than 1.

A closed system was prepared for the circulation of molecular oxygen. Bymeans of this system the oxygen, withdrawn from a 10 liter gasometer bymeans of a circulating pump and dried, was fed to the reaction vesseland, when leaving the latter through the condenser at 78 C., was washedwith an aqueous KOH solution and recycled to the starting gasometer. Thereaction was started by activating the U.V. lamp, keeping theperfiuoropropylene at a temperature between 65 C. and 75 C., and byfeeding oxygen through it at a flow rate of about 50 liters/hour.

After 11 hours, 2.4 liters of oxygen had been absorbed. At this pointthe reaction was stopped and the unreacted perfiuoropropylene wasremoved from the reactor by distillation at 30 C. It contained about0.3% of epoxide.

17.0 g. of a liquid-semisolid product were obtained as the residue,which analyzed as: C=l9.83%; F=62.73%; O=17.44%.

These data are very close to the average formula s 6 2)n- The N.M.R.spectrum showed that this substance consisted essentially of CF(CF )-CFgroups that were bonded to each other by the oxygen bridges prevailinglyof the O-O (peroxidic) type and only in part by O- (ether) bridges. Itfurthermore was shown by the N.M.R. spectrum that the terminal groupswere essentially OCF and OCOF in a 1:1 ratio and in such amounts as tolead to the formula (C F O with a value of n equal to about 40.

The presence of oxygen in the peroxidic form was also demonstrated byiodometric titration carried out as pre- 14 viously described. Thereresulted 7.8 g. of active oxygen per 100 grams of product, whichcorresponded to 0.9 atom of active oxygen per C 1 unit.

The polyperoxide of perfluoropropylene thus obtained was remarkablystable at room temperature. When heated in the pure state to atemperature above 70-80 C., it decomposed in a violent manner byevolving gaseous and low-boiling products, leaving practically no liquidresidue.

EXAMPLE 7 Under reaction conditions as described in Example 6, butoperating at a temperature of 29 C. and with a molecular oxygen flow of20 liters/hour, a photochemical oxidation of 505 g. ofperfluoropropylene was carried out for 22 hours. At the end of thereaction, by distillation of the unreacted olefin, there were obtained71 g. of a liquid acid product having a high viscosity at roomtemperature and a percent composition corresponding to the formula (C FO The N.M.R. analysis showed that the chain consisted prevailingly of CF units bonded by ether and peroxidic bridges in a ratio of about 1:1.There were also present in the chain CF O units in a ratio to C 'F unitsof about 1:15.

The terminal groups present were mainly groups with minor amounts of CF--OC-F O and CF OCF(CF )O- groups and also, in decreasing amounts, O'CFCF (CF 3 OCOF,

The iodometric analysis was in agreement with a content of 0.5 atom ofactive oxygen per C -F unit present in the chain.

This product showed an acidimetric equivalent weight of 1000, asdetermined by prolonged agitation of a sample with a cold 0.1 N NaOHsolution and a back titration of the unreacted excess alkali and of thehydrolyzed fluoride ions of the COF groups.

This example shows that, by varying certain conditions as compared tothose described in Example 6 (more particularly, by increasing theirradiation time and the reaction temperature), it is possible to obtainproducts having an intermediate composition between that of apolyperoxide and that of a polyether of perfiuoropropylene.

EXAMPLE 8 This example was carried out in the same manner as thatdescribed in Examples 6 and 7 with a U.V. lamp having an emission of 0.9watt in order to carry out a photooxidation of 700 grams ofperfluoropropylene at a starting temperature of --30 C., using an oxygenfeed flow rate of 20 l./h.

The photooxidation was carried out for a period of 560 hours while thetemperature increased until a temperature of 10 C. was attained. At thispoint there were obtained, after evaporation of the unreacted monomerand of the volatile reaction products, 560 grams of a polymeric producthaving a percent composition corresponding to the formula (C F O andcontaining (by iodometric analysis) 0.08 atom of active oxygen per C F Ounit.

This example shows that it is possible to obtain polyether products witha low peroxidic bridge content directly from the reaction, by increasingthe irradiation time and consequently the conversion degree (which inthis case was higher than 70%) even though an irradiation index I lowerthan 1 is employed.

EXAMPLE 9 This example demonstrates that, although using a relativelyhigh irradiation intensity, it is possible to obtain polyether productscharacterized by a high content of peroxidic groups, provided that theprocess is carried out so as to maintain in the reaction zone a lowconversion of C -F for example lower than 20%. It is desirable for thispurpose to carry out the process in a continuous manner, for example asfollows.

An apparatus was prepared which comprised a 0.5 liter consistsubstantially of a neutralization with alkali and of thermaldecomposition of the salts, thus eliminating the carboxylic groups andmost of the peroxidic bridges, as follows. 600 g. of KOH (85%) in theform of pellets were introduced into a 3 liter vessel provided with anglass reactor, containing a liquid phase of perfiuoropro- 5 agitator, areflux condenser and a charging tube. The pylene, in which thepreviously described Q81 Hanau vessel was heated to 100 C. and the slowintroduction type high-pressure mercury-vapor U.V. radiation generof thecrude oil was started, while vigorously agitating. ator was immersed.With these conditions, the average The temperature rose to 130-140 C.while, within 6 irradiation index was about 4 watts/emi A dipping tube10 hours, the introduction of 2.0 kg. of fluorooxygenated to the bottomof the reactor permitted the introduction of product was completed. Thesalt that formed was kept an oxygen flow which then left the reactor,through a under agitation for a further 24 hours at a temperaturecondenser kept at -78 C. The unreacted oxygen was of about 140 C. Byeliminating the circulation of washed with alkaline solution and setinto a 50 liter gaswater from the reflux condenser, the water containedometer from which, by means of a circulating pump, it in the vessel wasthen permitted to distill together with was continuously reintroduced,after drying, into the a small fraction of neutral low boilingfluorooxygenated photochemical reactor. The amount of oxygen consumedoils while the inner temperature rose to 320-330 C. in the reaction wasperiodically replenished in the system. During this stage, the evolutionof a considerable amount To the photochemical reactor, aperfluoropropylene of gas, mainly consisting of CO was observed.

flow was also continuously fed from a 50 liter gasometer After a furtherperiod of 4 hours of heating at 300- by means of a circulating pump. 320C., the content of the reactor was cooled and The level of the liquidphase in the reactor was mainthe oil previously steam-distilled wasadded. All the tained constant by a continuous discharge, through theliquid contained was then filtered to remove the solid bottom, of acorresponding amount of liquid, which was salts, prevailingly consistingof KF. In total, 1,350 g. sent to acontinuous fractionated distillationsystem. From of neutral fluorinated oils were obtained, which were thissystem, the olefin and the compounds, if any, boiling fractionated bydistillation into the fractions having the below 20 C. were recycled asgases to the gasometer characteristics reported in the following table.

TABLE 2 Average molecular Fractions Distillatlonrange G. Compositionweight I 50100 C./1 mm. Hg 460 031101.00 600-1,000 IL--. 100 C./(). 1mm. 555 CaFoO 1, 000-2, 000

200 am. 1 mm. III 200 C./(). 1 mm. 300 CaFaOLos 2, SOD-3,500

350 o./0. 05 mm.

IV Residue CsFaOrm 5,000

and the liquid reaction products were collected separately. The reactedperfluoropropylene was periodically replenished in the system.

With the described apparatus, a reaction was carried out by initiallyintroducing into the reactor 600 g. of C 1 and by feeding through it, ata temperature of to 30 C., an oxygen flow of 80-100 liters/hour and aperfluoropropylene flow of about 100 liters/hour. After 42 hours, 330 Nliters of oxygen were adsorbed and 2,850 g. of polymeric liquid productswere obtained. Analysis of the residual C F in the system showed that itcontained 22.2% by weight of epoxide C F O, corresponding to aproduction of 190 g. of epoxide.

The liquid product obtained had the following average composition:C=21.l4%; F=66.93%; O=11.93% corresponding to the formula (C3F501 27)Determination of molecular weight resulted in a determination that theinteger n in the above formula had an average value between 10 and 15.N.M.R. and iodometric analyses showed that the product consisted of amixture of low polymers formed prevailingly of a repetition of -CF-CF(CF units bonded to each other by ether and peroxidic bridges thatwere present in 4:1 ratio. The neutral terminal groups of the chainswere -'O'--,

and CF --OCF(CF )O groups in the respective ratios of 10:3:1, whereasthe terminal groups of acidic nature consisted of OCF --CF(CF )O-COF,-O-CF(CF )CF -OCOF, -OCF O-COF, and O-CF --COF in the respective ratiosof l0:3.5:l:0.5.

As described hereinbelow, from the acid products obtained as describedabove which contain a certain amount of peroxidic groups, it is possibleto obtain neutral products having a very high thermal and chemicalstability by suitable treatments. A treatment of this type may All thesefractions exhibited no oxidizing power and presented an exceptionalchemical stability. In the infrared absorption spectrum of theseproducts, the presence of bands characteristic of acid groups could notbe observed.

The spectroscopic analyses by N.M.R. showed that the structure of thechain was virtually the same as the structure of the chain of thestarting product; however the structure of the terminal group A(fluoroformate isomer groups) had been changed to a mixture of CF H andCFHCF in a ratio of about 3:1.

EXAMPLE 10 The photochemical reaction was carried out in a glasscylindrical reactor having a diameter of 245 mm. and a volume of 22liters, in the center of which there was placed coaxially a mercuryvapor lamp of the Hanan No. 5661 type, consisting of a tubular quartzwell (sheath) having a diameter of 46 mm. and a length of 250 mm.containing an irradiating quartz element of the TQ1200 type which emitsa total of 34 watts of radiations having a wave length lower than 3,000A.

In the reactor there were also placed a dipping tube reaching the bottomfor the introduction of oxygen, a thermometric well (sheath) immersed inthe liquid phase, a gas outlet tube, and another dipping tube forrecycling C F The gas outlet tube was connected to a condenser kept at-78 C. by a mixture of a alcohol and Dry Ice. The condensate wasrecycled to the reactor through the aforedescribed dipping tube whilethe residual gaseous mixture was passed to a washing system wherein itwas bubbled first through water and then through a 40% aqueous KOHsolution. To the washed gas thus obtained there was added fresh comingfrom a gas reservoir (in order to replace that absorbed by the reaction)and, after careful drying over concentrated H 80 the whole was passedback, by means of a circulation pump, and bubbled into the reactor. Theentire 17 reaction system thus described was filled with oxygen, and25.75 kg. of liquid C F (at its boiling point) were charged into thereactor. Thereafter, while circulating oxygen at a fiow-rate at 1,000l./h., the lamp was switched on.

After about 10 minutes, the absorption of oxygen commenced with aninitial rate (measured by a metering device inserted at the gasreservoir outlet) of about 250 l./h.

The reaction was carried out for 17 hours, during which time thetemperature of the liquid phase gradually rose from 30 C. to 10 C. andthe absorption rate gradually decreased until it reached a minimum rateof 50 l./ h. A total of 2,280 liters of oxygen had been consumed(measured under room condition). At this point the lamp was switched offand the reaction mixture was slowly heated to 30 C., while collectingand condensing the gaseous products distilling from the reactor. Theyweighed 6.60 kg. and consisted of unreacted perfiuoropropylene (76.2%)and of the epoxide of perfluoropropylene (18.8%). The gaseous mixturealso contained small amounts of products having a higher boiling point,which were found to be analogous to those which the successive fractionconsisted of.

The residual mixture remaining in the reactor was then heated to 100 C.,while bubbling oxygen through it in order to facilitate the removal oflow-boiling compounds, and was kept at this temperature for 3 hours,during which time there were distilled 640 g. of a mixture of productsessentially consisting of 130 g. of hexafluoropropylene, 25 g. ofepoxide, C F O, 30 g. of perfluoro-4-methyl-1,3- dioxolane,

(boiling point 8 C.), 110 g. of perfluoro-2,4-dimethyl-1,3- dioxolane,

o Fa-C F-C F1 \CC Fa (boiling point 32.5 C.) 52 g. ofperfluoro-1methoxyiso propyl fluoroformate,

o Fz-O-C F2C FO OF C Fa (boiling point 51 C.), 67 g. ofperfluoro-2-(5-methyl-4,7- dioxa)-octyl fiuoroformate,

o FsO(C F:|C FO)2 (boiling point 110-114 at 755 mm., 85 at 270 mm. Hg),and the higher homologues, more specifically, 75 g. of

CF3O(C Fz-C F-0)r-COF JFs (boiling point 155-8 at 755 mm., 82 C. at 35mm.), 25 g. of

C F3O(C Fr-C F O)4COF (boiling point 93-5 at 20 mm. Hg), and 20 g. of

(extrapolated boiling point, 225230 C. at 760 mm.).

At boiling temperatures intermediate with respect to those of theaforedescribed oligomers, there were present minor amounts of oligomersof analogous structure but characterized by the presence of thefollowing chain terminal groups (instead of CF O-):

More particularly, the following products were isolated:

o F3-0-0 F 0 (0 F2(') F-Oh-C 0 F wherein n=1 (boiling point -90 C.),wherein n=2 (boiling point 132-138 C.), and wherein n=3 (boiling point173-180 C.), and products belonging to the series wherein n=1 (boilingpoint -105 C.), wherein n=2 (boiling point 144-152 C.), and wherein n=3(boiling point 185192' C.).

Higher oligomers which were not separated from each other bydistillation were also present.

The residual oily product weighed 17.16 kg. and had an oxidizing powercorresponding to 0.37 active oxygen atom per 10 oxygen atoms containedin the oil and an experimental elemental composition of C F O Variousspectroscopic determinations and molecular weight determinationsindicated that these products had the prevailing average formula s s s1.o42) 14 with a ratio of terminal groups -0 FOO o F to o FzOCOFcorresponding to about 5.

N.M.R. analysis showed, however, that the average ratio of CF O units toC 'F O units in the molecules was about 1:20.

A sample (100 g.) of this product was subjected to distillation and thefollowing fractions were obtained: 5 g. with a boiling point between 60C. and 100 C. under atmospheric pressure; 19.3 g. with a boiling pointbetween 52 C. and 158 C. at a pressure of 20 mm. Hg; 69.1 g. with aboiling point between 98 C. at 0.1 Hg; and 344 C. at 0.7 mm .Hg; land aresidue of 1.6 g. that could only be distilled at higher temperatures.

The washing solutions (water and KOH) were mixed and analyzed. Theycontained 24 mols of CO 72 mols of HF, and 24 mols of trifluoroaceticacid.

This example thus illustrates that one may directly obtain reactionproducts with a very low peroxidic group content by reaction of C F with0 upon using irradiation conditions such that the I value Sl/2Vl/3 isgreater than 2. In this example this value as calculated is between 6and 7.

EXAMPLE 11 An apparatus was assembled consisting of a cylindricalstainless-steel reactor having a volume of 0.80 liter, a diameter of 70mm., provided with an inner tubular quartz well (diameter 20 mm. andlength mm.), a steel reflux condenser (cooled to 50 C. by circulation ofcold alcohol), a gas-inlet dipping tube and a thermometer well. Theassembly was so constructed as to withstand pressures of 10 atmospheres.A valve and a manometer placed on the top of the reflux condenserpermitted the reading and regulation of pressure.

A U.V. lamp of the type described in Example 1 was placed within thequartz sheath. In the reactor, air was replaced with oxygen. Then, bydistillation, 1,050 g. of perfluoropropylene were introduced and oxygenwas passed through the clipping tube to a total pressure of 7atmospheres, using for this purpose a cylinder provided with a pressureregulator, At this point, the lamp was switched on while keeping thereaction zone at -60 C. by means of an outer bath of alcohol and DryIce. After a few minutes, pressure in the reactor began to decrease. Thepressure was then kept at the desired value (7 atmospheres) by theintroduction of oxygen from the cylinder,

and this procedure was continued for 2 hours. At this point, the lampwas switched olf, the pressure was slowly released, and the gaseousproducts were evaporated. These essentially consisted of unreactedprefluoropropylene, 0.6 g. of the epoxide of perfluoropropylene and theoxidation products (COFfl-l-CFHOF) derived from 0.025 mols Of C3F5.

As the residue there remained 51 g. of an oily product having anoxidizing power corresponding to 0.65 active oxygen atoms per atoms oftotal oxygen contained, and having an average elemental composition ofwith an average molecular weight of about 8,200. In this example, thevalue of the index I was calculated to be higher than 3.

Thus, this example shows that by adopting sulficiently high irradiationintensities, it is possible to operate under an oxygen pressure markedlyhigher than atmospheric pressure Without obtaining appreciable formationof peroxidic products.

Moreover, since the operation was carried out at a low temperature,N.M.R. analysis showed the presence of only traces of the groups--O-CFa-O and O(|7FO CF; in the chain.

EXAMPLE 12 An apparatus was assembled consisting of a glass reactor inthe form of a cylinder and having a diameter of 80 mm. and a capacity of0.7 liter, containing coaxially therein a quartz tubular well having adiameter of 40 mm. In this well was placed a Hanau high pressure U.V.ray lamp of the TQ81 type, which emits a total of 3.8 watts ofradiations having wavelengths lower than 3,300 A. The reactor was alsoprovided with a thermometer, a gas-inlet dipping tube, and a refluxcondenser kept at 78 C. by means of an alcohol-Dry Ice mixture.

A system analogous to that described for Example 10 was employed forwashing, drying and recycling of the residual oxygen leaving the refluxcondenser (after introduction of make up to replace the consumedamount).

720 g. of perfluoropropylene were charged into the reactor and condensedby means of an outer bath. The temperature of the liquid was maintainedat about 32 C. and the U.V. lamp was switched on while contemporaneouslycirculating oxygen at a flow-rate of 100 l./h. After 1 hour and 35minutes, 10.7 liters of oxygen had been absorbed. The lamp was switchedoff and the gaseous and low-boiling products were distilled from thereactor.

The residual oily products amounted to 120 g. had an oxidizing powercorresponding to 0.52 active oxygen atoms per 10 total oxygen atomscontained and had an experimental elemental composition corresponding to3 5.95 1.18)n- The average value of a was between 10 and 20.

The gaseous and low-boiling products contained, in addition to unreactedperfluoropropylene, 9 g. of the epoxide of perfluoropropylene and minoramounts of the gaseous products described in Example 10.

The washing solution was found to contain 0.28 mol of HF, 0.09 mol ofperfluoroacetic acid, and 0.09 mol of CO For this example, the value ofthe index I 100 X E S1 2V1 s was calculated to be about 3 and, inaccordance with this value, the peroxidic group content of the totalproduct was very low.

0 EXAMPLE 13 The apparatus described in Example 12 was used, but thequartz well containing the lamp was replaced by a well of the same sizebut made of Pyrex glass.

715 g. of perfiuoropropylene were charged into the reactor, and anoxygen stream was bubbled in (100 l./h.), irradiation being carried outfor 4 hours and 15 minutes. A total absorption of 7.15 liters of oxygen(measured under room conditions) occured. The temperature of thereaction mixture was kept at about -32 C.

After having evaporated the volatile products at room temperature(consisting mainly of unreacted C F along with 6 g. of the epoxide ofperfluoropropylene), there remained as the residue an oily productweighing 74 g. and having an oxidizing power corresponding to 1.9 activeoxygen atoms per 10 atoms of total oxygen contained.

The elemental composition of this product was In this example, a filter(glass well) was used which, as shown by photometric measurementscarried out separately, eliminated of the radiations having a wavelength lower than 3,300 A. Since the luminous power penetrating thereaction system had thus been reduced to the value of I, which in thepreceding example was about 3, in this example was reduced to 0.3. Thus,this example shows that at this low value of I the oxidizing power ofthe product obtained was markedly raised.

EXAMPLE 14 An apparatus was employed which included a quartz test tubehaving a diameter of 18 mm. and a volume of 40 cc., provided with areflux condenser kept at ---78 C. with alcohol and Dry Ice, and with adipping tube for the introduction of gas. In contact with a side of thissmall reactor and arranged so that the two axes were parallel, there wasplaced an Hg-vapor lamp of the low pressure Pen Ray type (without use offilters). This lamp has, in the useful zone, an emission of 0.5 watt.

38 g. of perfluoropropylene were initially introduced into the quartztest tube, the lamp was switchedon, and bubbling of an oxygen steam (l0l./h.) was commenced. The irradiation was carried on for 5 hours.

The mixture was kept, during the whole reaction, at its boiling point.After having evaporated the volatile products at room temperature(essentially consisting of unreacted C F together with 0.1g. of theepoxide of perfluoropropylene), there remained at the residue an oilyproduct weight 11 g. and having an oxidizing power corresponding to 1.2active oxygen atoms per 10 atoms of total oxygen contained.

The experimental elemental composition of this product was C F O In thisexample, the experimental set up made it possible to use only /6 of theuseful U.V. light emitted by the lamp. Therefore the value of 1 wascalculated as about 0.75. Thus, this example demonstrates that, alsowith this geometry of the system, a low value of 1 corresponds to a highcontent of peroxid'ic groups.

EXAMPLE 15 (COMPARATIVE) The same experimental arrangement was used asin the preceding example, but instead of the low-pressure lamp, therewas employed a Pen Ray lamp provided with a suitable filter whicheliminated all of the U.V. radiations except those at 3,660 A. Thereactor, containing 40 g. of perfiuoropropylene, was then irradiatedwhile bubbling in an oxygen stream (10 1./h.) for 6 hours. Afterevaporation of the gaseous products, which essentially consisted of C Fno appreciable amount of oily product was observed. Thus, in thiscomparative example it was demonstnated that radiations having a wavelength of 3,660 A. were essentially ineffective for the preparation ofthe polyether products of the invention.

EXAMPLE 16 A photochemical oxidation was carried out using 35 kg. ofperfiuoropropylene kept in the liquid phase at a temperature of 40 to 35C. in a cyclindrical reactor (diameter 270 mm., length 250 mm.) in thecenter of which was a tubular quartz having a diameter of 46 mm. andcontaining an irradiating element of the Hanan TQ81 type, which emits atotal of 3.8 watts of radiations having a wave length lower than 3,300A. To the bottom of the reactor was passed a stream of dry oxygen (100l./h.). The gases leaving the reactor, after passage through a refluxcondenser cooled to -78 C., were recycled (after adding make up oxygento replace that amount consumed during the reaction, washing withalkali, and drying). The reaction was carried out for 110 hours, bywhich time 980 liters of oxygen had been consumed. By distillation ofthe: unreacted perfluoropropylene and the volatile reaction products,4.8 kg. of polyether products were obtained in the form of a thickviscous liquid. They had an average elemental composition correspondingto the formula C F O and a peroxidic group content corresponding to 2.1g. of active oxygen per 100 g. of product.

The N.M.R. spectrum and the molecular weight determinations correspondedto a general formula the ratio of these groups being 4:1. Thus, thisexample shows that it is possible to obtain polyethers having a highcontent of peroxidic groups at a degree of conversion not higher than20%, with a low irradiation index I (in this case between 0.5 and 1),even when this is primarily due to the use of a high ratio between thereactor volume and the energy omitted by the' UN. lamp. 1

EXAMPLE 17 1,070 g. of perfluoropropylene were introduced into astainless steel autoclave having an inner diameter of 70 mm. and avolume of 800 cc., and provided with a coaxial inner well of transparentquartz having an outer diameter of 20 mm. and a length of 185 mm., andwith a dipping tube for the introduction of oxygen, and with a stainlesssteel reflux condenser kept at a temperature of 80 C. The system wascapable of withstanding pressures of 20 atmospheres. By means of acylinder provided with a pressure regulator, oxygen was introducedthrough the dipping tube until an absolute pressure of 7 atmospheres wasreached. At this point, by utilizing a discharge valve placed after thecondenser, the oxygen flow leaving the reactor was adjusted to a rate of40 liters/hour, measured at atmospheric pressure, while, through acontinuous feeding of gaseous oxygen, the pressure inside the reactorwas kept constant at 7 atmospheres. An U.V. lamp of the high pressureHanau TQ81 type was introduced into the quartz well. By means of a bathplaced outside the autoclave, the temperature of the liquid phase wasadjusted to +10 C., the lamp was switched on and, by appropriateregulation of the outer bath, the temperature was kept at +10 C. for 2hours. With this irradiation arrangement, the index I was 4.4 watts/cm.

The outlet stream was bubbled through an aqueous KOH solution in orderto neutralize and thereby retain the volatile add products formed in thereaction.

At the end of the two hour period the lamp was switched off, thepressure was released, and the gases (unreacted C F together withperfluoropropylene epoxide) were washed in the alkaline solution.

645 g. of product containing 42 g. of perfiuoropropylene epoxide werethus collected. From the liquid product which remained in the reactor, afraction of 11 g., boiling at between 0 C. and 50 C., was separated bydistillation. This fraction prevailingly consisted of perfiuoro-4-methyl-1,3-dioxolane (B.P. 8 C.) and perfiuoro-2,4-dimethyl-1,3-dioxolane (B.P. 325 C.). The residue consisted of 298 g. ofan oily polymeric substance which, by elemental analysis, showed anaverage composition of 63.7% of F and 20.2% of C, corresponding to theformula CF O with an aver-age molecular weight of about 1,200. Byiodometric analysis (reaction with Nal in acetic anhyd-ride plus CFClCFCl and successive titration with thiosulfate of the iodinereleased), there was determined a content of 1.7 oxygen atoms combinedin peroxidic form per 10 atoms of ether oxygen contained.

By N.M.R. examination, this polymeric product was shown to consist ofpolyether chains containing -CF Ogroups together with C F-C Fr-O- ofwhich the first one was prevailing, and also by the presence of (2) acidterminal .groups of five types:

The gases leaving the reactor were washed with aqueous KOH solution,whereby it was determined that 156 g. of C F had been converted byoxidative demolition according to the reaction:

C F +O= CF COF+COF EXAMPLES 18 TO 24 By using the same apparatus asdescribed in the preceding example and by working analogously, a seriesof tests were carried out varying temperature and pressure of thereacting mixture.

The working conditions and the main data for the products obtained arereported in the following table. The characteristics of the polymericproducts were obtained from experimental analytical results, while theratios relating to the various structural units contained in thepolymeric chain were evaluated by examination of the N.M.R. spectrum, onthe basis of the aforementioned criteria.

Examples 24 is reported only for the sake of comparison. Thus, it showsthat when the photochemical oxidation is carried out at lowtemperatures, and more particularly at temperatures of about -55 orbelow, the polymeric chain forming the oily polyether product containsvirtually no units of the type -CF O- and -CF(CF )O-.

TABLE 3 Example number 18 19 20 21 22 23 24 Reaction conditions:

Temperature, C 22-24 2-i-2 19-12 -2+2 2 +1 85 -60-55 Absolute pressure,atm 7 7 5 3 3 1 Initial 03m, g 1, 070 1,070 1,000 1,000 1, 070 1, 005 1,040 Irradiation time, hours 2 2 2 2 2 2 2 Products obtained:

CaFs e oxide, g 127 8 92 18 84 13 0. 5 Polyet or products, g 135 335 180275 104 300 94 0 1% recovered, g- 700 060 750 688 810 705 945Characteristics of polyether prod- Composition by elemental analysisCFnuoo'sa CF1.oa n.w FmeOuo cFmOuo CFLWOD. CFmsOtua CFmaOoao Approx.average molecular weigh 1, 000 2, 000 1, 200 2, 500 2, 500 3, 000 6, 000Active oxygen content (act.

0; g./100 g. product) 0. 79 1. 04 1. 01 1. 64 0. 66 1. 30 0. 47 Averagestructure C FgO--(CsFs0)r-(C F:O)q

(C F O)S-(0)sI-A (Q+R)/P 0. 72 0. 28 0. 55 0.30 0. 33 0. 24 0. 01 R/Q 0.08 0. l0 0. 0. 08 0. 10 0. 10 0. 00 S/(P-i-Q-I-R-i-l)--- 0. 08 0. 11 0.17 0. 14 0.05 COF COF COF COF COF COF COF CFz-COF CFa-COF CFzCOF -OF;COCFg--COF CF3-COF Prevailing -c F-COF -o F-COF -c F-COF -c F-COF -o F-COF -c F-CO F F; F; C F 3 F; F 3 (I) F:

As will be apparent, changes and variations can be made in details, inpracticing this invention, without departing from the spirit thereof.

Having thus described our invention, what we desire to secure and claimby Letters Patent is:

1. A method of preparing COF CF COF, the epoxide of perfluoropropolene,cyclic ethers having the formula X F R C F-O- units to the total C F -Ounits being from zero to 2, and the ratio of total active peroxidicoxygen units to the total C F O-- units being from zero to 1, said chaincontaining at least one C F O unit and having as terminal groups at oneend a CF -O-- radical linked to said chain through a carbon atom and atthe other end a radical selected from the group consisting of COF,CFr-COF and CFCOF which method comprises photochemically reacting in theliquid phase a reaction mixture consisting essentially ofperfluoropropylene and molecular oxygen at a temperature between about100 C. and +80 C. and a pressure between about 0.1 and 40 atmospheres inthe presence of ultraviolet radiation containing at least 1% ofradiations of a wave length lower than 3300 A., the amount of oxygenbeing such that the liquid phase is continuously saturated therewith.

2. The method of claim 1 carried out in the absence of a solvent ordiluent for the perfluoropropylene.

3. The method of claim 1 wherein there is present in said liquid phasean inert halogen-containing solvent.

4. The method of claim 1, wherein the temperature is between and +40 C.and the pressure is between 0.5 and 10 atmospheres.

5. The method of claim 1 wherein the ratio of total active peroxidicoxygen units to the total -C F O units is between zero and 0.2, saidmethod being carried out using an average irradiation intensity I,wherein I is defined as follows:

wherein E is the amount in watts of UV. radiations having a wave lengthlower than 3,300 A. which penetrate the reaction system having a volumeof V(cm. through a transparent surface of S(cm. of between 2 and 50watts/cmP, and wherein the reaction is carried out until the degree ofconversion of perfluoropropylene is at least 5%.

6. The method of claim 5 wherein the average irradiation intensity I, isbetween 3 and 20 watts/cm 7. The method of claim 1 wherein the ratio oftotal active peroxidic oxygen units to the total C F ,O'- units isbetween 0.2 and 1, said method being carried out using an averageirradiation intensity I, wherein I is de fined as follows:

X E S /2V1/3 wherein E is the amount in watts of UN. radiations having awave length lower then 3,300 A. which penetrate the reaction systemhaving a volume of V(cm. through a transparent surface of S(cm. ofbetween 0.1 and 2 watts/cmfi, and wherein the reaction is carried outuntil the degree of conversion of perfluoropropylene is from about 0.1to about 70%.

8. The method of claim 7 wherein the average irradiation intensity I, isbetween 0.3 and 1.5 watts/cm.

9. The method of claim 1 wherein the ratio of the sum of the total --CFO units and total units to the total C F --O units is between 0.05 and2,

said method being carried out at a temperature between l0 and +80 C.

10. The method of claim 9 wherein said ratio of the sum of the total -CF--O- units and total -C FO-- units to the total C F O- units is between0.1 and 1 and wherein said temperature is between 0 and +50 C. 11. Themethod of claim 10 wherein the ratio of the sum of the total CF O- unitsand total (i} F O.

units to the total C 'F O- units is between zero and 0.1, said methodbeing carried out at a temperature between 100 and 0 C.

12. The method of claim 11 wherein said ratio of the sum of the total CF-O-- units and total units to the total -C F -O- units is between zeroand 0.05 and wherein said temperature is between 80 and 40 C.

References Cited UNITED STATES PATENTS 3,451,907 6/1969 Sianesi et a1.204-l58 3,525,758 8/1970 Katsushima et a1. 204-458 HOWARD S. WILLIAMS,Primary Examiner v UNITED STATES PATENT OFFICE CERTIFICATE 0F CQRRECTIONPacenc'No- 3,704 14 m November 28, 1972 i flgmalo SIANESI, ADOLFOPASETTI, and COSTANTE CORTI It is certified that error appears in theabove-identified patent and that said Letters Patent are hereincorrected as shown below:

I Column 2, line 45 "polymerising" should read '--p y i Hi2s,---. I

Column 3, lines 20-24, the structural formula CB-Ci-cri should re ad'error-on J J xwl'fl' Column 3-, linef33: "chain."' should read-'-chain;--; o Column 3, line 35: "-COF, -0F -COF and -cF'(c --co1?,"

should read -coF, -CF -C0 F and -cF (cF )--c0F; j o .,1smn 3, [1 1- 169; "an" should read rand.

- T lymm5 ml. 1 "Ulis s-. 11 i h uld.r al;.:ryi;ili ins+-; at" I *T l Il 5,

line 46: "penetrate" should read "penetrate the".

Column 5, line 48: "volumes" should read "volume"; Column5, line 66:"resource" should read "recourse"; .Column 6, line 6 "acterises" shouldread -acter:|'.zes--;

. l ne 8: .o,12e r92i ie s ld r -2.

L- u v j .J

Page 2 $27 8 UNITED STATES PATENT OFFICE 3 CERTIFICATE OF CQRRECTIONPatent No. 3,70 4 Datea November 28, 1972 flQDARIO SlANESI, ADOLFOPASETTI, and .COSTANTE CORTI It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 9, line 52: "and the" should read "and, therefore, the--; Column9, line 67: uratioffl should read --rat:lo--. Column 10, line 56: "50 g,fraction" should read "-50 g. of fraction". vColumn lll2, Table I, lastcolumn, line 7, under the letter "F": "63,0" should read -68.0",

v a Column 13, line 67: "by the oxygen" should read -by oxygen--. Column16, line 8: "crudeoil" should read crudeacid oil";

, Column 17,

line 14: "condition" should read -=-conditions--; Column 17-, line 74:after the structural formula a --period should appear. Column 18, line17: "atoms" should read --atoms--; Column 18, line 55: "liter, shouldread "liter and,

line 'value of a" should read -v alue.fo n- Column 20, line 49:"remained at" should read --remained as--; Column 20, line 50: "weight"should read "weighing";

Column 21, line]: "quartz having" should read --quartz well having"; 7Column 21, line 53: "20 mm. should read --26.nm1.-.. Column 23-24, Table3, under the heading "Average structure": "CF O (C F O) (CF 0)Q (cro) s-(o) SI-A CF Should read J Petenr'No. 3 3 704-, 214

Page} 111mm STATES PATENT oF ICE V CERTE HQATE CQRRECTEQN Dated November28, 1972 Inventofls) DARIO 'SIANESI, ADOLFO PASETTI, and COSTANTE CORTIIt is certified that; error appears in the ehove==identified patent,

and that said! Letters Patent are hereby corrected as shown below:

1 000 should read 1=-L06==-L Table 3, column 2 EDWARD MOFLETCHER R.

Table 3, under column 18, on the line C F recovered; g": ""700" shouldread "760- Table 3 und r column 19; on the line "C 1 recovered, g": "O60should read -660--v=. Table 3, under column l9, on the line g.,/100g.product)": "1.04" should read --164-- Table 3 under column 20", on

the line" llempera'tmre, C": "19-12" should read 9109 12",

I Table 3, under column 20, on the line "Initial" C F g":

"1 000" should read "1,080". Table 3, under column 20, on the line"analysisY"; 0 should read ----CF 00 Table 3, under column .21, on theline "Initial C F g"? 2 on the "688 should read 685". Table 3, undercolumn 21, on the line "(Q-hm/P": V0.30" should read eOc36===- Table 3,under column 22, on the line Poilyether product's, g": 104 should read--164- Table 3, Table 3, under column 23, on the line "Initial "(2 F g":1,005' should read "1 065"; Table 3, under" coiumn 23, on

line 2"--;of "Prevailing structure of QF f -CQF" reai line "C F6recovered g":

Signed e r- Sealed s 19th day of March 19m. .J

(SEAL) Attest:

Go MARSHALL DANN I Commissioner of Patents Attesting Officer

